Synthesis of 4,5-disubstituted benzo[c] [2,7]naphthyridines as precursors of pyrido[2,3,4-kl]acridones and related natural products

A methodical investigation on functionalization by carbonylated groups in p osition 4 and 5 of the benzo[c] [2,7]naphthyridine skeleton has been undert aken. In particular the study has shown the complex influence of these two sites on each other. A careful choice of both substituents in 4 and 5 permi tted the synthesis of an interesting pyrido[2,3,4-kl]acridone tetracyclic s tructure through an intramolecular Mukayama aldolisation reaction. The stru cture is supposed to be a potential precursor to various marine alkaloids o f the pyridoacridine family.